Tubular drill string members



March 17, 1964 F. K. FOX 3,125,173

TUBULAR DRILL STRING MEMBERS Filed Oct. 12, 1961 2 Sheets-Sheet 1 Free Fax INVENTOR.

ATTOR/VEVJ March 17, 1964 F. K. FOX 3,125,173

TUBULAR DRILL STRING MEMBERS Filed Oct. 12, 1961 2 Sheets-Sheet 2 Fred A. Fax

INVENTOR.

United States Patent OfiFice 3,125,173 Patented Mar. 17, 1964 3,125,173 TUBULAR DRILL SE'RWG MEMBERS Fred K. Fox, 242 Stoney Creek, Houston, Tex. Filed Oct. 12, 1961, Ser. No. 144,663 6 Claims. (Cl. 175-323) This invention relates to improvements in tubular members, such as drill collars and drill pipe, which form parts of a drill string for use in the rotary drilling of oil and gas wells. More particularly, it relates to such a tubular drill string member which, as disclosed in my US. Patent No. 2,999,552, is so formed as to reduce the area of its periphery engageable with the well bore, and thereby lessen the likelihood of its becoming stuck due to difierential pressure thereacross.

In the preferred form of the invention described in this patent, the periphery of the tubular member is grooved along one or more helical paths which distribute the reduced thickness of the member. uniformly along its length so as to avoid stress concentrations therein. More particularly, each such helical path extends from its upper to its lower end in the direction of rotation of the drill string. As mentioned in my earlier patent, this direction of the helix causes the peripheral surface of such member between the grooves to have a propeller effect in the heavy drilling mud or against the well bore, thereby converting a portion of the frictional force on the collar due to its rotary movement into a longitudinal force effective to increase the Weight load on the bit.

It has been found, however, that when such tubular members are sized to at least substantially fill the well boreas, for example, in the case of very large collars in the drilling of deep wells-the propeller action may cause them to rotate during trips into and out of the bore aswell as during drilling. This makes the drill string especially hard to handle at the wellhead, and in fact may cause such members to become disconnected by unthreading.

An object of this invention is to provide a tubular drill string member of this general type in which the helical grooves are so arranged thereon as to minimize the tendency for it to rotate during its trips.

This as well as other objects are accomplished, in accordance with the illustrated embodiments of the present invention, by means of a tubular drill string member in which longitudinally successive helical grooves in the outer periphery thereof angle in opposite directions with respect to its axis. Thus, the tendency for the grooves which extend in the direction of rotation of such member to rotate such member during its trips into and out of the bore is counteracted by those grooves extending in the opposite direction. More particularly, the longitudinally successive grooves are of substantially equal length and angular disposition with respect to the axis of said tubular member so as to substantially balance the forces tending to rotate themember during its trips. In a still further preferred form of the invention, the opposite ends of longitudinally successive grooves are interconnected to form a continuous fluid path along the member, which is particularly useful in washover operations.

In the drawings, wherein like reference characters are used throughout to designate like parts:

FIG. 1 is a longitudinal view of part of a conventional drill collar extending through a well bore and having a portion thereof engaged against a side of the bore;

FIG. 2 is a cross-sectional view of the drill collar and bore, taken substantially along broken line 22 of FIG. 1;

FIG. 3 is a longitudinal view, partly in section, of a drill collar constructed in accordance with the present invention, and with an intermediate portion thereof broken away;

FIG. 4 is a cross-sectional view of the drill collar of FIG. 3, as seen along broken line 44 of FIG. 3;

FIG. 5 is a cross-sectional view of a modified form of the drill collar shown in FIGS. 3 and 4; and

FIGS. 6A and 6B are longitudinal views, also partly in section and broken away, of a joint of drill pipe constructed in accordance with the present invention.

Turning HOW to a detailed description of the abovedescribed drawings, FIGS. 1 and 2 illustrate the problem with which tubular drill string members of the type contemplated by the present invention are concerned. More particularly, these figures show a conventional type of drill collar 11 having a portion 12 of its cylindrical periphery engaged with a side of a well bore 13. In the drilling of an oil or gas well, the space within the bore and about the drill collar is filled with a drilling mud which has a high specific gravity so that it will normally be at a hydrostatic pressure greater than the pressure of the formation adjacent thereto.

As is apparent from FIGS. 1 and 2, the differential in pressure between the drilling mud and that of the formation is effective over an area determined not only by the length of the portion 12 of the collar, but also by the peripheral arcuate portion of such portion transcribed by the angle theta. If this area is large, as it well may be, and the pressure differential is of considerable magnitude, it is quite possible that there would not be suflicient power available at the wellhead or tensile strength in the upper unstuck portions of the string to produce an axial lifting force suiiicient to overcome this radial force such that the collar will remain stuck. An example of the force which may be encountered is set forth in my earlier patent. Although the problem has been described herein particularly in connection with a drill collar, it obviously also pertains to the drill pip'e'connected in the drill string above the collars. V

As shown in FIGS. 3 and 4, the drill collar 14 constructed in accordance with the present invention comprises an elongate, thick-walled tubular member 15 connected in a drill string at its upper and lower ends. More particularly, the upper end of this tubular member has a threaded box 16 for connection with a threaded pin 17 on the lower end of a drill pipe '18, and the lower end is provided with a threaded pin 19 for connection with a threaded box 20 of another such collar or, as shown, a bit sub 21 which connects the collar with any suitable rotary type bit 22. Generally there will be more than one drill collar connected between the drill pipe and bit although, for purposes of illustration, it is sufficient to merely show and describe the single collar 14.

As is apparent from the drawings, the diameter of the ungrooved periphery of the tubular member 15 is uniform from one end to the other, although this invention contemplates that the ends of such member above and below the grooved area thereof (to be described) may be slightly larger or smaller than the ungrooved area intermediate between such grooves. In any case, the maximum diameter of the collar is less than that of the bit 22 so that an annulus is formed between the well bore and the collar during the drilling operation.

There are a number of helical grooves 23 in the outer periphery of the tubular member 15, each such groove being shallow so as to provide a maximum of area adapted to be held out of engagement with the well bore with only a minimum loss of weight and strength. More particularly, and as shown in FIG. 4, each such groove 23 has a base which forms, in a section transversely of the tubular member, a line which is fiat between its intersection at opposite ends with the periphery of the tubular member. However, I contemplate that the base of the groove may form, in the aforementioned cross section, a line which departs somewhat from flat in that it may be slightly concave or, on the other hand, convex, as illustrated by the grooves 24 of the modified form of drill collar 14a shown in FIG. 5.

Obviously, the specific configuration of the grooves in the tubular member may vary with a number of other factors, such as the width thereof as well as the number of grooves intersecting the periphery of the tubular member along any cross section thereof, as long as such tubular member accomplishes the basic purpose of the invention in reducing the likelihood of differential pressure sticking while maintaining its basic functionsuch as weighting the bit in the case of a drill collar.

As illustrated in FIGS. 4 and 5, there may be three equally circumferentially spaced-apart grooves '23 in any section across the grooved area of the collar. Thus, in a drill collar having a 6% inch O.D., a groove having a flat base and being inch deep at its intermediate point will have a peripheral length about 2.55 inches, so that the three grooves will circu-mscribe approximately 38.3 percent of the total periphery of the collar. This would, in the average case, thereby reduce the force holding the collar against the well bore at least approximately a corresponding percentage. At the same time, a drill collar having the OD. above mentioned and a 2 /8 inch I.D. would still be approximately 1 inches thick at its thinnest point adjacent the deepest portion of a groove, so that its weight per lineal foot would be reduced only from approximately 91 pounds to approximately 86 /2 pounds.

It will also be appreciated that, as described in connection with the tubular drill string member of my earlier patent, an annular type blowout preventer may be sealed about the collar 14 despite the grooves formed therein. That is, since these grooves are substantially flat, the rubber sealing member of such blowout preventer will flow into them. This particular configuration of the grooves also lessens the likelihood of mud caking up within them as the drill collar is rotated within the well bore.

As shown in FIG. 3, longitudinally successive ones of the helical grooves 23 are angled in opposite directions with respect to the axis of the tubular member 15 so as to form a zigzag or serpentine grooved area from one end to the other of the grooved area of the tubular member. As can also be seen from FIG. 3, the longitudinally successive grooves are of substantially equal length and form substantially equal angles with respect to the axis of the tubular member. As previously indicated, this at least substantially balances the tendency for the tubular member to rotate in opposite directions during its trips into and out of the well bore. Thus, theoretically at least, the tubular member will move upwardly and downwardly within the well bore without turning, thereby making the string much easier to handle at the wellhead and avoiding the possibility of the tubular members becoming unthreaded from one another.

As can also be seen from FIG. 3, the circumferentially spaced-apart grooves are disposed parallel to one another so that the serpentine paths of grooves formed by longitudinally successive ones of said grooves are also disposed and arranged parallel to one another. This, of course, distributes the reduction in wall thickness and thus the stress uniformly along the length as well as about the circumference of the collar.

Still further, and again as previously indicated, the opposite ends of longitudinally successive grooves are interconnected to form a continuous zigzag or serpentine grooved path from one end to the other of the grooved area of the collar. This preserves another advantage of the preferred form of the drill collar shown in my earlier patent in that it provides a continuous fluid bypass particularly useful in washover operations.

The joint of drill pipe 25 illustrated in FIGS. 6A and 613 also comprises a tubular member as, although such tubular member has much thinner walls than the tubular member 15 of which drill collar 14 is comprised. A tool joint is welded or otherwise secured to each opposite end of the tubular member 25, in this case a threaded box 27 being welded to the upper end of such member and a threaded pin 2% being welded to the lower end thereof. As in the case of the drill collars previously described, the joint of drill pipe 25 has an area between grooves intermediate its opposite ends which is of uniform diameter and equal to or either slightly smaller or slightly greater than the diameter at such opposite ends.

Similarly to the drill collars illustrated in FIGS. 3 to 5, the drill pipe 25 has a plurality of shallow helical grooves 29 cut in the periphery thereof, with longitudinally successive grooves angling in opposite directions with respect to the axis of the tubular member 26. Also, as in the case of the previously described drill collars, longitudinally successive helical grooves are interconnected at their opposite ends to form continuous zigzag or serpentine grooved paths along the length of the pipe. More particularly, there are three equally circumferentially spaced-apart grooves 29 in any section crossing the grooved area of the pipe, with such helical grooves being parallel to one another to provide parallel serpentine or zigzag grooved paths. Obviously, then, the outer circumference of this drill pipe would appear, in any cross section along the grooved length thereof, as does the outer circumference of the drill collars shown in either FIG. 4 or 5, depending on the particular configuration of the base of the grooves 29;.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is:

1. An integral, elongate tubular member having means at its opposite ends for connection above the drill bit in an oil or gas well drill string and a plurality of helical grooves in its outer periphery and arranged longitudinally thereof, longitudinally successive ones of said grooves angling in opposite directions with respect to the axis of said tubular member.

2. A tubular member of the character defined in claim 1, wherein longitudinally successive grooves are of substantially equal length and form substantially equal angles with respect to said axis.

3. A tubular member of the character defined in claim 2, wherein the opposite ends of longitudinally successive grooves are interconnected to form a continuous grooved path.

4. A tubular member of the character defined in claim 1, wherein there are equally circumferentially spacedapart grooves disposed parallel to one another.

5. A tubular member of the character defined in claim 1, wherein the opposite ends of longitudinally successive grooves are interconnected to form a continuous grooved path.

6. A tubular member of the character defined in claim 5, wherein there are equally circumferentially spacedapart grooves disposed parallel to one another.

References Cited in the file of this patent UNITED STATES PATENTS Hinderliter Mar. 8, 1932 Froome et a1 June 17, 1941 Nater Feb. 7, 1956 Fox Sept. 12, 1961 FOREIGN PATENTS Belgium Feb. 15, 1958 

1. AN INTEGRAL, ELONGATE TUBULAR MEMBER HAVING MEANS AT ITS OPPOSITE ENDS FOR CONNECTION ABOVE THE DRILL BIT IN AN OIL OR GAS WELL DRILL STRING AND A PLURALITY OF HELICAL GROOVES IN ITS OUTER PERIPHERY AND ARRANGED LONGITUDINALLY THEREOF, LONGITUDINALLY SUCCESSIVE ONES OF SAID GROOVES ANGLING IN OPPOSITE DIRECTIONS WITH RESPECT TO THE AXIS OF SAID TUBULAR MEMBER. 